1. Field of the Invention
The present invention relates to an optical multiplexer/demultiplexer which multiplexes or demultiplexes signal light in a wavelength division multiplexing optical communication system and the like.
2. Related Background Art
In a wavelength division multiplexing (WDM) optical communication system which multiplexes signal light having a multitude of wavelengths and tansmits thus multiplexed signal light through an optical transmission line, an optical multiplexer/demultiplexer which multiplexes or demultiplexes signal light having a multitude of wavelengths is used. The optical multiplexer/demultiplexer disclosed in U.S. Pat. No. 5,960,133 (Document 1) is favorably used in an optical communication network which can select ports for inputting or outputting individual wavelength components, while making signal light transmission paths and signal light wavelengths flexible.
The optical multiplexer/demultiplexer disclosed in Document 1 comprises a wavelength branching device for spatially splitting the individual wavelength components included in light fed into an input port, and a rotary mirror for arbitrarily choosing an output port to output each wavelength component split by the wavelength branching device. Namely, an output port which is an output destination for each wavelength component is determined by an angle of rotation of the rotary mirror.
FIG. 1 is a schematic view of a conventional optical multiplexer/demultiplexer disclosed in Document 1. In the conventional optical multiplexer/demultiplexer 9, light emitted from an end face of an optical fiber 11 is collimated by an optical system 111, so as to be made incident on a diffraction grating device 121, and is diffracted by the diffraction grating device 121 by different diffraction angles for respective wavelengths, so that different wavelengths are outputted to their respective optical paths. The individual wavelength components (λ1 to λ3), outputted from the diffraction grating device 121, are condensed by an optical system 112.
The wavelength component λ1 condensed by the optical system 112 is reflected by a mirror reflector 131 disposed at a light-condensing position thereof, so as to be fed into the optical system 112 again. The wavelength component λ2 condensed by the optical system 112 is reflected by a mirror reflector 132 disposed at a light-condensing position thereof, so as to be fed into the optical system 112 again. The wavelength component λ3 condensed by the optical system 112 is reflected by a mirror reflector 133 disposed at a light-condensing position thereof, so as to be fed into the optical system 112 again.
The respective wavelength components reflected by the mirror reflectors 131 to 133 and then fed into the optical system 112 are collimated by the optical system 112, so as to be fed into the diffraction grating device 121, and then are diffracted by the diffraction grating device 121, so as to be fed into the optical system 111. The wavelength components fed from the diffraction grating device 121 into the optical system 111 are condensed by the optical system 111, so as to be made incident on any of the optical fibers 11 to 13.
The optical multiplexer/demultiplexer 9 allows each wavelength component emitted from an optical fiber end face to be made incident on any optical fiber end face, and can arbitrarily select entrance/exit optical fibers by setting angles of inclination of the mirror reflectors 131 to 133.